Systems are found throughout the world for managing delivery of liquids from a storage tank to a contained space such as a tank or other container. Typically, a pump is provided to pressurize the liquid as it is being delivered, but gravity may also be used on occasion. For example, fuels such as gasoline or diesel fuel are delivered by a pump from a storage tank to vehicle fuel tanks. While the invention can be used for a variety of liquids, we feet at this time that it will be most useful for liquid fuel delivery.
Such delivery occurs most frequently at retail gas stations where end users (motorists) manage the delivery themselves. Liquid fuel delivery will be used as the example to explain the invention. Other types of liquids and systems may be able to take advantage of the invention as well.
Colloquially, the term “gas pump” is used to refer to the entire fuel delivery unit. To avoid confusion, hereafter we will use the term “pump system” to refer to the entire device that pumps, meters, and controls fuel flow to a vehicle or other fuel holding tank. The term “fuel pump” or “gas pump” refers to the actual pump that pulls and pressurizes liquid fuel contained in a larger storage tank.
In a pump system, the fuel pump provides pressurized fuel to a metering system that determines the amount of fuel that flows during a fuel delivery event. The pressurized fuel is supplied to a manually operated fuel nozzle through a hose. Fuel nozzles are used to safely manage this fuel delivery. The decades-old design still in use for fuel nozzles has an internal main fuel valve that is manually operated by a motorist with an external lever. Fuel flowing from the valve passes through a spout inserted into a filler pipe of the vehicle, and then into the tank to be filled. The motorist wishing to fill a fuel tank operates the lever to control and stop fuel delivery.
Fuel nozzles now usually include a detent to hold the lever in one of several positions providing various rates of flow. A sensor detects imminent overflow and releases the detent to prevent spillage. These sensor mechanisms work quite well in shutting off fuel flow before spillage occurs.
However, small amounts of fuel usually remain in the nozzle and particularly, the spout after the main valve closes. When the motorist removes the spout from the filler pipe, this fuel can drop to the ground or drip on the paint surrounding the filler pipe. This fuel escaping from the spout after the main valve closes is a safety hazard, causes both air and ground pollution, and can damage the paint around the filler pipe. Accordingly, this fuel escape is undesirable, and should be minimized.
A number of different systems have been developed over the years to reduce this fuel escape. U.S. Pat. Nos. 5,337,729 and 6,331,742 for example provide check valves at the end of the spout to retain fuel within the spout after the main valve has closed.